[ICOM] Receive antenna input?

[Gary Fiber]

Bob,

You can do that but be aware there is no switching that antenna input 
out of line when you transmit. A few have had the receiver input 
blown out if the transmitting antenna is too close or when using high power.
You can simply protect that input by switching that antenna using a relay.

Proper way would be to use a antenna relay something like an old Dow 
Key relay those were built to handle RF and usually had coaxial connections.
.
Realistically a nice automotive 12 volt relay will do too. Basically 
you are building an amplifier keying relay circuit but connecting the 
receive antenna through the normally closed contacts.
The 775 has 12 volts available and the PTT pin goes low when 
transmitting so connecting the relay coil across those pins on the 
acc jack will cause a normally closed relay or its normally closed 
contacts to open when you transmit removing the antenna from that 
receive input.

I would suspect a lot on this list have done this and will likely 
have more to say.

Gary K8IZ







At 07:50 AM 9/30/2006, you wrote:
>I have an IC-775.
>
>In the operators manual on page 11 number 2 it talks about the back 
>panel of the radio.
>Number 2 is talking about the
>"Receive Antenna Jacks" [RX ANT IN]/[RX ANT OUT]
>
>It says:
>"Located between the transmit/receive switching  circuit and 
>receiver's RF stage. Connect an external preamp or RF filter, if
>desired."
>
>That is all that is mentioned about this back panel item.
>
>Question is can I connect an external receive only antenna to this 
>point (a loop for 160) and if so does anyone know how?
>
>   73 fer nw,
>Bob AD5VJ(AAR6VM)
>http://www.ad5vj.com/
>
>Member: CTDXCC, NTCC
>FISTS: # 12637
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>
>
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Gary Fiber K8IZ
GROL PG-19-6691
Washington State Resident